/******************************************************************************
 *                                                                             *
 * License Agreement                                                           *
 *                                                                             *
 * Copyright (c) 2003 Altera Corporation, San Jose, California, USA.           *
 * All rights reserved.                                                        *
 *                                                                             *
 * Permission is hereby granted, free of charge, to any person obtaining a     *
 * copy of this software and associated documentation files (the "Software"),  *
 * to deal in the Software without restriction, including without limitation   *
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 * and/or sell copies of the Software, and to permit persons to whom the       *
 * Software is furnished to do so, subject to the following conditions:        *
 *                                                                             *
 * The above copyright notice and this permission notice shall be included in  *
 * all copies or substantial portions of the Software.                         *
 *                                                                             *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR  *
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,    *
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 * DEALINGS IN THE SOFTWARE.                                                   *
 *                                                                             *
 * This agreement shall be governed in all respects by the laws of the State   *
 * of California and by the laws of the United States of America.              *
 *                                                                             *
 ******************************************************************************/

#include "inc/altera_avalon_spi_regs.h"
#include "HAL/inc/altera_avalon_spi.h"

/* This is a very simple routine which performs one SPI master transaction.
 * It would be possible to implement a more efficient version using interrupts
 * and sleeping threads but this is probably not worthwhile initially.
 */

int alt_avalon_spi_command(volatile void * base, uint32_t slave,
                           uint32_t write_length, const uint8_t * write_data,
                           uint32_t read_length, uint8_t * read_data,
                           uint32_t flags)
{
  const uint8_t * write_end = write_data + write_length;
  uint8_t * read_end = read_data + read_length;

  uint32_t write_zeros = read_length;
  uint32_t read_ignore = write_length;
  uint32_t status;

  /* We must not send more than two bytes to the target before it has
   * returned any as otherwise it will overflow. */
  /* Unfortunately the hardware does not seem to work with credits > 1,
   * leave it at 1 for now. */
  uint32_t credits = 1;

  /* Warning: this function is not currently safe if called in a multi-threaded
   * environment, something above must perform locking to make it safe if more
   * than one thread intends to use it.
   */

  IOWR_ALTERA_AVALON_SPI_SLAVE_SEL(base, 1 << slave);
  
  /* Set the SSO bit (force chipselect) only if the toggle flag is not set */
  if ((flags & ALT_AVALON_SPI_COMMAND_TOGGLE_SS_N) == 0) {
    IOWR_ALTERA_AVALON_SPI_CONTROL(base, ALTERA_AVALON_SPI_CONTROL_SSO_MSK);
  }

  /*
   * Discard any stale data present in the RXDATA register, in case
   * previous communication was interrupted and stale data was left
   * behind.
   */
  IORD_ALTERA_AVALON_SPI_RXDATA(base);
    
  /* Keep clocking until all the data has been processed. */
  for ( ; ; )
    {
    
      do
        {
          status = IORD_ALTERA_AVALON_SPI_STATUS(base);
        }
      while (((status & ALTERA_AVALON_SPI_STATUS_TRDY_MSK) == 0 || credits == 0) &&
             (status & ALTERA_AVALON_SPI_STATUS_RRDY_MSK) == 0);

      if ((status & ALTERA_AVALON_SPI_STATUS_TRDY_MSK) != 0 && credits > 0)
        {
          credits--;

          if (write_data < write_end)
            IOWR_ALTERA_AVALON_SPI_TXDATA(base, *write_data++);
          else if (write_zeros > 0)
            {
              write_zeros--;
              IOWR_ALTERA_AVALON_SPI_TXDATA(base, 0);
            }
          else
            credits = -1024;
        };

      if ((status & ALTERA_AVALON_SPI_STATUS_RRDY_MSK) != 0)
        {
          uint32_t rxdata = IORD_ALTERA_AVALON_SPI_RXDATA(base);

          if (read_ignore > 0)
            read_ignore--;
          else
            *read_data++ = (uint8_t)rxdata;
          credits++;

          if (read_ignore == 0 && read_data == read_end)
            break;
        }
    
    }

  /* Wait until the interface has finished transmitting */
  do
    {
      status = IORD_ALTERA_AVALON_SPI_STATUS(base);
    }
  while ((status & ALTERA_AVALON_SPI_STATUS_TMT_MSK) == 0);

  /* Clear SSO (release chipselect) unless the caller is going to
   * keep using this chip
   */
  if ((flags & ALT_AVALON_SPI_COMMAND_MERGE) == 0)
    IOWR_ALTERA_AVALON_SPI_CONTROL(base, 0);

  return read_length;
}
